A. Field of the Invention
The present invention relates to the administration of a cosmeceutical preparation to the skin of a subject. More particularly, the present invention relates to the transcutaneous delivery of a cosmetic agent in solution using iontophoresis.
B. Background of the Invention
As used hereinafter, the expression “cosmetic agent” refers to substances administered to the skin of a subject to alter appearance, to enhance vitality, or to otherwise facilitate subsequent cosmetic undertakings. Thus, the expression “cosmetic agent” includes skin numbing substances that reduce skin sensation in preparation for aggressive cosmetic procedures, such as surface abrasion, hair removal, or tattoo erasure.
One method for delivering a cosmetic agent in a cosmeceutical solution into the skin of a subject involves coating the skin of the subject over an intended treatment region with the cosmeceutical solution and allowing the cosmetic agent in the solution to penetrate the skin by osmosis and by any related spontaneously occurring mass transport phenomena.
If a cosmetic agent in a cosmeceutical solution possesses ionic properties, then a more sophisticated technique for delivering the cosmetic agent uses electrical energy to induce the cosmetic agent to penetrate the skin. This is called iontophoresis.
Iontophoresis affords enhanced control over the rate of delivery of the cosmetic agent and over the depth of the penetration by the cosmetic agent into the skin of the subject. Additionally, iontophoresis can induce larger molecules of a cosmetic agent to penetrate the skin than would be possible by merely coating the skin with a solution containing that cosmetic agent.
Iontophoresis involves the application of an electromotive force to drive a cosmetic agent into the skin. An iontophoretic system includes two electrodes that engage the surface of the skin at respective locations that are distanced from each other. One of these electrodes is positioned with a supply of the cosmetic agent on the skin within the intended treatment region; the other is positioned on the skin beyond the intended treatment region.
During iontophoresis, direct electrical current is used to cause ions of the cosmetic agent to cross the surface of the skin and to diffuse into underlying tissue. The surface of the skin is not broken by this administration of the cosmetic agent. When conducted within appropriate parameters, the sensations experienced by a subject during the delivery of the cosmetic agent in this manner are not unpleasant.
The direct current employed in an iontophoresis system may be obtained from a variety of electrical power sources. These include diminutive disposable batteries carried on one of the electrical contacts used in the iontophoresis system, paired regions of contrasting galvanic materials that when coupled by a fluid medium produce minute electrical currents, and electrical hardware powered by sizable consumable or rechargeable batteries or through electrical cord interconnection to a wall socket.
The bulk, weight, and cost of electrical hardware powered by sizable consumable or rechargeable batteries or through electrical cord interconnection to a wall socket necessitate that such electrical hardware be configuration as equipment distinct from either of the electrical contacts that are applied directly to the skin to administer a cosmetic agent iontophoretically. Accordingly, power sources that are driven by sizable consumable or rechargeable batteries or through electrical cord interconnection to a wall socket limit the mobility of the subject during the time that treatment is in progress. Still, such power sources are advantageously robust and are, therefore, capable of effecting the iontophoretic delivery of a given quantity of cosmetic agent at a faster rate than is available using other sources of direct current.
A flow of electrical current requires an uninterrupted, electrically-conductive pathway from the positive pole of a power source to the other, negative pole thereof. Living tissue is made up primarily of fluid and is, therefore, a conductor of electrical current. In an iontophoretic circuit, the opposite poles of a power source are electrically coupled to respective, separated contact locations on the skin of the subject. The difference in electrical potential created by the power source between those contact locations causes a movement of electrons and electrically charged ions through the skin between the contact locations
In an iontophoretic delivery system, the polarity of the net overall electrical charge on dissolved molecules of a cosmetic agent determines the nature of the electrical interconnection that must be effected between the power source that is used to drive the system and the supply of the cosmetic agent that is positioned on the skin at one of the contact locations used by the system. A positively charged cosmetic agent on the skin of the subject is coupled to the positive pole of the power source. Correspondingly, a negatively charged cosmetic agent on the skin of the subject must be coupled to the negative pole of such a power source. Examples of common iontophoretically administrable cosmetic agents in each category of polarity are listed in the table below.
Positive PolarityNegative PolarityCosmetic AgentsCosmetic AgentsLidocaineAcetic acidVitamin ARetinyl palmitateTocopheryl acetateTocopherolGlucosideMandelic acid
An iontophoretic circuit for driving a cosmetic agent into the skin is established by coupling the appropriate pole of the power source through the cosmetic agent on the skin at the treatment region where the cosmetic agent is to be administered. Simultaneously, the other pole of the power source is coupled to a location on the skin of the subject that is distanced from the treatment region. The coupling of each pole of the power source is effected by the electrical connection of each pole to a respective of the two electrodes of the iontophoresis system. The electrode at the treatment region is referred to as the active electrode; the electrode at the contact location on the skin distanced from the treatment region is referred to as the return electrode.
An iontophoresis system does not require intensive skin site sanitation to avoid infections. Patches and the other equipment used in iontophoresis do not interact with bodily fluids and, accordingly, need not be disposed as hazardous biological materials following use. With some exceptions, no pharmacologically significant portion of a cosmetic agent delivered iontophoretically becomes systemically distributed. Rather, a cosmetic agent delivered iontophoretically remains localized in the tissue at the site of administration.
The dosage of a cosmetic agent delivered iontophoretically is conveniently and accurately measured by monitoring the amount and the duration of the electrical current flowing during the administration. With electrical current being measured in amperes, and with time being measured in minutes, the dosage of a cosmetic agent given transcutaneously is given in units of ampere-minutes. Due to the minute quantities of cosmetic agent required in iontophoresis, the dosage of a cosmetic agent administered by iontophoresis is frequently specified in the smaller unit of milliampere-minutes.